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Discussion Starter · #1 · (Edited)
Hello,

I'm 215 pounds, I do track days, and I bottom out my front forks

The tension compression seems to be ok, but the preload is garbage.

I am looking for some info on what kind of spring would be good for my use case, which is heavy braking at the end of straightaways.

I am not sure if a spring that is soft at first, then tenses up is the right move, or a spring that is more linear would work best.

My bike has not had its forks serviced in years, I assume since it was new. I'll be doing maintenance on the forks at the end of the season.

Also, if anyone has any recommendations for a rear spring, or a cheap(ish) non oem replacement of the whole shock, I'll look into that too.

Thanks
 

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I remember years ago (90's) when Progressive springs were the Best thing since sliced Bread, Now not so 👀
The first street bike I owned that I paid for brand new off the showroom floor, was a 1985 Honda VF1100S. Amongst many other technological 'marvels' was a system on the fork called TRAC. I don't remember what the acronym stood for, I just know that it wasn't making things better at the front of the bike.

You could think of it as a hydraulic damping circuit which was supposed to make the damping stiffer if you really hopped on the brakes so the fork wouldn't bottom out. Considering that was a damping rod 'conventional' fork, adding complexity to get better response and missing the mark shouldn't have been a surprise to me. If I recall correctly it also had Schrader valves in the fork tops so you could adjust the air pressure to fine tune when the compression of that gas so you would be in control of the 'rising rate' that resulted from the air volume getting compressed as the front end became more loaded.

20 years later, I bought a brand new 2005 Yamaha FZ6. You would call that one a Fazer, as it had the half fairing. Conventional fork, rising rate springs.... piss poor damping rates for anything more spirited than straight line commuting. Very vague feeling in corners.... numb, is the best word I can use to describe it. That got progressively worse, as the level of fuel in the tank was reduced. The amount of bobbing about on the fork made for eerie directional control...... but it was happening over a range of fork travel of less than an inch in most cases. If you got on the brakes hard enough to engage the higher rate portion of the spring, you had already consumed more than half of the available suspension travel. Until you got to the higher rate spring, everything was inconsistent. Once you did, the limited fork travel would upset the tire on any sort of irregularity.

The difference in that FZ6 fork after installing .95 Kg linear springs, and having the damping reworked was a revelation to me. From that point forward, I could tell exactly how much braking force I was feeding into the front end, by how much the front end was compressing. Much more predictable, much more comfortable, and far, far more enjoyable.

I also installed an Ohlins TTX shock on the thing and between the two the handling was corrected. There's really no other way to say that. It finally handled the way it should.

The OEM setup on my '09 ZX6, was about 90% of what I had gotten the FZ6 to when I bought it in '12 and figured out what settings everything needed to be at. I don't know if the springs are linear in the fork, I have had them apart a number of times to service the seals, etc. and don't see the characteristic change in spacing I would expect to see with a rising rate setup. I think they are 1.0 Kg springs which are a tiny bit more harsh than I would consider ideal, but I can work with it for the street riding I do..... now that I have a Penske rear shock on the thing (setup for my weight and use) as well as freshly serviced seals in the fork, the ZX6 is unquestionably the best handling bike I have owned.
 

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I’ve had.85, .9 linear fork springs in bikes that weigh similar amounts, with me at similar weight. Conventional and USD, they provided a more stable performance throughout the entire suspension stroke. If all I have on the street is 4” and change, I much prefer to have as much of that available as possible.
 

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Discussion Starter · #9 ·
I’ve had.85, .9 linear fork springs in bikes that weigh similar amounts, with me at similar weight. Conventional and USD, they provided a more stable performance throughout the entire suspension stroke. If all I have on the street is 4” and change, I much prefer to have as much of that available as possible.
I'll take a closer look at those then, I don't want a squishy ride, but I also don't want to be riding a bike that feels like a old school bobber
 

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That's the beauty of single rate springs..... if the spring is correct, then getting the damping to work consistently is much simpler. I think the fork springs in the '09 ZX6 are probably 1 Kg/mm and they're nearly too stiff for my street riding.
 

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Discussion Starter · #11 ·
Update:
Have not bought anything for this.
can anyone confirm that the front forks only need these two kits to do a rebuild:

You might not get the product for the zx6r, I pre-selected my bike, so it shows as compatible.

I am also looking at other sites and brands to get the most reliable parts, not that I can see much of a difference so far.

The race tech site recommends a 1kg/mm spring for the front and a 11kg/mm for the rear, for track days, does that sound correct?
 

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Discussion Starter · #13 ·
I believe the consensus is OEM far outperforms AllBalls…..
Fair enough.
I assume that since you commented only on the brand, that the seals and bushings kit is all I need (minus new fluid) to do the fork maintenance.
I'll buy the springs from a site that has both front springs, and the rear shock spring.

The bushings + seals I'll buy from a local kawi dealership.
 

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OP, I don’t recall which model bike you’re planning on working on. There are specific tools needed which change by model. Some can be homemade…. Lloyd and others recommended which tools I would need and they have paid for themselves many times.
 

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Discussion Starter · #16 ·
OP, I don’t recall which model bike you’re planning on working on. There are specific tools needed which change by model. Some can be homemade…. Lloyd and others recommended which tools I would need and they have paid for themselves many times.
A 2013 zx6r.
I want the suspension to be more biased towards the track.
I bought a .95kg/mm front spring kit, and a 10.7kg/mm rear spring, with the plates the site said it needed to fit onto my rear shock.

There are at least 2 tools I'll need, but I am going to see if I can use things I already have, or if I can make the tools. No sure how that will go.
 

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The seal driver pays for itself the first time you use it.
Having the syringe with the calibrated depth setting to assure the correct oil level removes any doubt about it. I did also purchase the bullet to guide the seals onto the fork legs…. I don’t think that it would be possible to build up the leg without damaging the seal without something to smooth out the transition.
 
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